I have a dual energy system - Gas Furnace (heil, about 15 years old) and a 2 year old Lennox heat pump.

When the temperature gets colder than about -7C, the heat pump will often startup, run for 10 to 20 seconds then shut off - then the gass furnace will kick in

I live in an area with an incentive program for electricity and a sensor that automatically switches off the heat pump at -13C.

The heat pump is not iced up, defrosts normally.

It seems that the heat pump is telling the gas furnace that something is wrong, kicking off and telling the gas to start up? Does a system like this contain a mechanism of this sort??

Any thoughts would be appreciated before I call a tech - would like to have an idea of what could be wrong.

yuri

02-22-2009 06:01 PM

May have lost a lot of Freon and is cutting out on a low pressure control. Call a Lennox tech B4 more damage is done.

kennzz05

02-23-2009 05:21 AM

most of us are not using the metric system so please use farenheit conversion (sorry im too lazy to convert it myself) or just post both values, thanks

beenthere

02-23-2009 06:40 AM

-7C=19.4F
-13C=8.6F

I use conversion Plus, from MRHVAC.com.
Its free, and does close to 100 other conversions.

dac122

02-23-2009 08:03 AM

At the temps you mentioned it is not unreasonable for your aux to kick on exclusively. That brief short-cycle is wasteful and may affect the longevity of your equipment. Get a pro and have him check out the system.